docs: def _define_fit_param_names(self):
          """
          Convenience function to define mappings between the names of the
          columns in the initial guess table (and the name of the fitted
          parameters) and the actual name of the parameters in the model.
  
          This method sets the following parameters on the ``self`` object:
          * ``pars_to_set`` : Dict which maps the names of the parameters
            initial guesses to the actual name of the parameter in the
            model.
          * ``pars_to_output`` : Dict which maps the names of the fitted
            parameters to the actual name of the parameter in the model.
          """
  
          xname, yname, fluxname = _extract_psf_fitting_names(self.psf_model)
          self._pars_to_set = {'x_0': xname, 'y_0': yname, 'flux_0': fluxname}
          self._pars_to_output = {'x_fit': xname, 'y_fit': yname,
                                  'flux_fit': fluxname}
  
          for p, isfixed in self.psf_model.fixed.items():
              p0 = p + '_0'
              pfit = p + '_fit'
              if p not in (xname, yname, fluxname) and not isfixed:
                  self._pars_to_set[p0] = p
                  self._pars_to_output[pfit] = p